Method and apparatus for grooving the barrel of a plasticating machine

ABSTRACT

A method and apparatus for cutting grooves onto the interior surface of the barrel of a plasticating machine in order to increase the friction against sliding unmelted resin particles. The helical screw is removed from the barrel without removing the barrel from its operating site. A grooving device is transported from a remote location to the plasticating operation site and mounted within the barrel with a portion protruding from the barrel. A brance is attached to the end of the barrel to help support the grooving device. Periodic adjustments are made to the grooving device by manual or automatic manipulation of the grooving device.

This invention relates to a method and apparatus for machining grooveson the interior surface of the barrel of a plasticating extrudermachine, injection machine or blow molding machine.

In these plasticating machines, a screw rotatable within a barrel forcesheated resinous material from the inlet end of the barrel to a mold atthe outlet end of the barrel. The plasticating machine receives polymerpellets or powder of various particle shapes at the inlet end, heats andworks the polymer sufficiently to convert it to a melted or plasticstate and delivers the melted polymer under pressure through arestricted outlet or die. It is desirable that within the barrel theextrudate be fully melted and homogeneously mixed and uniform intemperature and viscosity.

In the plasticating machine, the barrel is an elongated cylinder whichmay be heated at various locations along its length and the screwextends coaxially through the barrel. The screw has a core with ahelical flight which cooperates with the cylindrical surface of thebarrel to define a helical valley for passage of the resin to theextruder outlet opening or injection front chamber.

At the inlet of the machine, the resin is unmelted. Generally, allsurfaces over which the unmelted resin passes are smooth, and thissmoothness can cause slippage of the resin particles with respect to theinside surface of the barrel. It has been known that this slippage canbe corrected by imparting roughness to the inner surface of the barrel.The increase in friction due to the roughness will tend to reduce theslippage of the resin particles with respect to the inside of the barreland will induce a more positive forward conveying action.

In the past, roughness was imparted to the interior surface of aplasticating machine barrel by removing the screw from the barrel anddismantling the heaters and heater shrouds and other fixating equipmentand then transporting the barrel to a remote shop for machining groovesinto the interior surface of the barrel. This machine operation requiredoperating downtimes of the plasticating machine extending for weeks ormonths.

In accordance with this invention, the interior surface of aplasticating machine is grooved by transporting a grooving device from aremote location to the plasticating extrusion operating site, ratherthan vice versa. This saves dismantling time at the plasticating machinebecause the heaters, shrouds, supports, and barrel, etc., need not beremoved. This also saves shipping costs because the grooving device isgenerally considerably lighter in weight than the barrel. When thegrooving device reaches the extrusion site, the screw is removed fromthe interior of the barrel and the barrel interior can then be cleaned.The barrel can remain installed on the extruder or injection machine andretain the operational mooring or support used during the plasticatingoperation and that support can then be used in turn to also support thebarrel with the grooving device. Thereby, no additional support need beerected for the grooving device but the plasticating barrel itself or anextension from the barrel can provide support for the grooving device.In this arrangement, the interior surface of the barrel can be groovedand the extruder or injection machine returned to operation with adowntime of no more than about a day or even only half of a day, ascontrasted to downtimes of weeks or months when the barrel istransported to a grooving device at a remote shop where custom groovingis performed.

The invention will be more completely understood by reference to theaccompany drawings in which

FIG. 1 is a plan view showing the general operational positioning of aplasticating injection machine;

FIG. 2 is a plan view of a plasticating extruder cylinder in combinationwith a portable grooving device, with the extruder cylinder remaining inits operational position;

FIG. 3 is a plan view of an injection machine with a portable groovingdevice, with the extruder rotated about a swivel on one end at theinjection machine to receive the grooving device;

FIGS. 4A and 4B present a side view of a grooving device-extruder barrelcombination, broken into two longitudinal fragments;

FIG. 5 is an exposed view of a honing head operatively positioned in anextruder barrel;

FIG. 6 is a view through the section 6--6 of FIG. 5;

FIG. 7 is a longitudinal sectional view showing the attachment of thegrooving device to the extruder barrel;

FIG. 8 is a view through the section 8-8 of FIG. 7; and

FIG. 9 is a cross-sectional view of a grooved interior of an extruderbarrel.

FIG. 1 schematically shows plasticating injection barrel 10 positionedat the plasticating operational site and surrounded by heater elementsschematically indicated at 12. A rotating screw, not shown, is disposedwithin barrel 10 to convey plastic through barrel 10. Hopper means 14 isprovided for feeding plastic pellets or powder to inlet port 16 ofbarrel 10, shown in FIG. 2. Driving means not shown, for rotating thescrew is located at the feed end of barrel 10.

FIG. 2 generally indicates a grooving device 18 having reciprocatingmotive means 20, such as a hydraulic reciprocating piston. Groovingdevice 18 is secured to adapter 22 on the discharge end of extruderbarrel 10, by means more clearly illustrated in FIGS. 7 and 8. FIGS. 7and 8 show adapter 22 is secured to barrel 10 by a plurality of bolts24. Bushing 26 is secured to adapter 22 by means of a plurality of bolts28. Bushing 26 has an inturned collar portion 30 having a plurality ofcircumferentially spaced interior slots 32, 34 and 36 shown in FIG. 8.As shown in FIGS. 7 and 8, longitudinal guide tube 38 has alongitudinally extending key 40 to be received in any one of slots 32,34 or 36, which is shown keyed into slot 34 in FIGS. 7 and 8.

Referring now to FIGS. 4A and 4B, longitudinal guide tube 38 whichextends coaxially within barrel 10 encloses an elongated interiorcoaxial rod 42. Guide tube 38 is subjected to longitudinal reciprocatingmotion by piston in cylinder motive means 20. Rod 42 is longitudinallymovable independently of guide tube 38. Manual rotation of handwheel 44actuates a conventional thread mechanism to longitudinally extend orretract rod 42.

FIGS. 5 and 6 illustrate the mechanism actuated by rod 42. FIG. 5 showsbarrel rim 48 with bolt openings for the attachment of a feed block, notshown, and rear portion 46 of barrel 10 which has overhead feed opening50 for the admission of plastic pellets or powder from said feed hopperduring operation of the extruder. The helical screw has been replaced bya grooving device in the figures. The grooving device has cutting head52 at its forward end. The outside surface of cutting head 52 isprovided with a plurality of elongated stone cutters 54. Stone cutters54 can be radially extended or retracted relative to the surface ofhoning head 52 by rotation of handwheel 44 and longitudinal movement ofrod 42, as explained below. When stone cutters 54 are in the retractedposition, they can be below or flush with the surface of head 52. Whenstone cutters 54 are in the extended position they extend outwardly fromthe surface of cutting head 52 and are urged against inner surface 56 offront portion 46 of barrel 10.

Referring to FIG. 6, each stone 54 is cam loaded from beneath by meansof a cam, not shown, with each cam held in place by means of a floatingpeg 58 located between its associated cam and longitudinal rod 42. Rod42 can have a longitudinally inclined surface or longitudinal taper, notshown, so that when rod 42 is thrust forward by rotation of handwheel 44its forward motion is transferred into radial movement pushing pegs 58outwardly which in turn moves a cam associated with each peg 58 which inturn urges cutting stones 54 radially outwardly into an extendedposition and against inner surface 56 of barrel extension 46. When rod42 is returned to a retracted position by reverse rotation of wheel 44,the force of the cam is released and a pair of spring loaded clips 60and 62, shown in FIG. 5, urges each cutting stone 54 to return to aretracted position with respect to the exterior surface of honing head52.

FIG. 5 shows honing or cutting head 52 in almost its most extendedpractical position at which edge 64 of cutting stone 54 has not reachedfeed opening 50. Actually, cutting head 52 can extend further to aposition whereat one-half of stone 54 is within the zone of feed opening50.

FIGS. 4A and 4B and FIG. 7 illustrate the attachment of reciprocatingmotive means 20 to the already described structure. Reciprocating motivemeans 20 can comprise a hydraulic piston, not shown, to which hydraulicoil is supplied through tube 66 from a source not shown. Oil of reducedpressure can be exhausted through tube 67. For reverse movement ofmotive means 20, the oil path is reversed. The hydraulic piston isprovided with piston extension rod 68 having universal joint 70 at itsforward end. Pipe brace 72 has a plurality of side cutout windows 74,76, 78 and 80 to reduce weight and to provide manual access to itsinterior and is equipped with forward and rear flanges 82 and 84,respectively. Forward flange 82 is secured to adapter 22 on extruderbarrel 10 by means of bolts 86, shown in FIG. 7. Rearward flange 84 issecured to a forward adapter 88 of reciprocating motive means 20.Thereby, the entire grooving device forward of (to the right of)universal joint 70 can be preassembled and inserted into extruder barrel10 so that the longitudinal and angular position of the grooving devicebecomes fixed within the barrel.

The inserted portion of the grooving device will be supported andcentered by collar 30 of bushing 26 with key 40 mated into any one ofslots 32, 34 or 36. Then, tube 72 can be mounted onto barrel 10 bybolting forward flange 82 to adapter 22. Finally, reciprocating motivemeans 20 is mounted on the assembly by inserting reciprocating rod 68into the open rearward end of pipe brace 72 to complete the universaljoint and securing forward adapter 88 to rearward flange 84. Thereby,open pipe 72 serves as a supporting brace for the rearwardly protrudingportion of the grooving device. Open windows 74, 76, 78 and 80 in pipebrace 72 in addition to reducing weight allow manual access to theinterior of pipe brace 72 to secure the opposite portions of universaljoint 70 to each other.

Open windows 74, 76, 78 and 80 also permit access to accomplish atperiodic intervals manual grasping of the grooving device in order toturn wheel 44 to radially force cutting stones 54 against barrel surface56 followed by actuating reciprocating means 20 to hone grooves intointerior barrel surface 56. Then, the reciprocating means is turned offand wheel 44 is turned in the opposite direction to retract stones 54from barrel surface 56. The grooving device is again manuallymanipulated through the windows, or otherwise, to withdraw longitudinalkey 40 from its particular slot 32, 34 or 36 and to return key 40 toanother of the slots, so that the circumferential position of cuttingheads 54 is changed. Then, wheel 44 is again turned to again urgecutting heads 54 against barrel interior surface 56. Thereby, there is asequential series of steps following each reciprocating cuttingoperation including manual retracting of cutting stones 54 and rekeyingof the grooving device into a different particular slot 32, 34 or 36,followed by again urging cutting stones 54 against the interior surface56 of the extrusion barrel. Thereupon, reciprocating motive means 20 isagain actuated to hydraulically reciprocate the entire grooving device,so that stones 54 cut another set of grooves into the interior surfaceof barrel extension 46.

Some of the above steps can be performed automatically, rather thanmanually. For example, stones 54 can be automatically extended andretracted relative to barrel surface 56, rather than manually. If stones54 are extended and retracted automatically, the extension andretraction can occur without turning off the reciprocating means.

The above sequence of steps is repeated after each set of grooves is cutso that the device is eventually operated with key 40 in each one ofcircumferentially spaced slots 32, 34 and 36, respectively. In theapparatus shown, there are four equally spaced cutting heads 54 andthree equally spaced circumferential slots 32, 34 and 36 so that, asshown in FIG. 9, at the end of the grooving operation there will betwelve equally spaced parallel grooves 90 cut into the interior surface56 of barrel extension 46. It will be appreciated that a differentspacing of the slots or a different number of slots or cutting headswill provide a different number and spacing of grooves 90. After theabove sequence is repeated three times, one time for each slot, thecutting heads are finally retracted and the grooving device is removedfrom the barrel. The screw can then be returned to the barrel and thebarrel can be returned to its plasticating operation without shipping itto another location and with no resetting of its support moorings.

It is a feature of this invention that the grooving device is light inweight so that it can be manually carried to the site of operation ofthe extruder, in contrast to the extruder being transported to the siteof the grooving device. The extruder barrel is generally of much heavierweight than the grooving device so that transport of the barrel to aremote shop would be more difficult and costly than transport of thegrooving device to the site of plasticating operation of the barrel.

FIG. 3 illustrates one means of adjusting the position of theplasticating machine at its operating site so that space will beprovided to position the protruding portion of the grooving deviceincluding tube brace 72 and reciprocating motive means 20. As shown inFIG. 3, the plasticating machine is rotated in place about pivot pointor swivel 92 on apron 93 so that the plasticating machine retains itsoperational support during the grooving operation. It is a furtherfeature of the invention that brace 72 finds support by attachment tobarrel 10, whereby the entire grooving device is supported upon theoperational bearings of the plasticating extrusion apparatus.

I claim:
 1. A method for machining grooves on the interior surface ofthe barrel of a plasticating machine having a rotating screw, saidmethod comprisinga. removing said screw from said barrel, b.transporting a grooving device having radially adjustable cuttingelements to the plasticating operating site of said barrel, c. insertingone end of said grooving device into said barrel so that the cuttingelements are disposed within said barrel at one end of the barrel andthe other end of said grooving device including reciprocating motivemeans extends outwardly from said barrel at the other end of saidbarrel, d. fixing the angular and longitudinal position of the groovingdevice within said barrel, e. attaching to said barrel at said other endof said barrel a support brace with said brace providing support forsaid other end of said grooving device, f. adjusting the radial positionof said cutting elements, and g. subjecting said grooving device toreciprocating movement to cut grooves into the interior surface of saidbarrel.
 2. The method of claim 1 wherein said grooving device includes arotatable wheel and an associated longitudinal rod for urging saidcutting elements radially against the interior surface of the barrel andmanually rotating said wheel to longitudinally move said rod and in turnto urge said cutting elements against said interior surface.
 3. Themethod of claim 1 wherein the angular and longitudinal position of saidgrooving device within said barrel is fixed by inserting a bushinghaving circumferentially spaced slots into said barrel at said other endof said barrel and keying said grooving device in one of said slots andat intervals of operation sliding the key out of one slot and intoanother slot by manual movement of said grooving device to rotate theposition of said cutting elements.
 4. A method for grooving the interiorwall of the barrel of a plasticating machine, said machine when inoperating position for extrusion having an internal rotatable screw andexternal heaters, said method comprising,a. removing said screw fromsaid barrel without changing the location of said barrel or said heater,b. transporting to said barrel a portable grooving device having cuttingheads on one end, c. inserting said grooving device into said barrelwith the end having said cutting heads inserted first, d. locking saidgrooving device against rotational movement in said barrel, e. mountingon said grooving device adjusting means to accomplish radial extensionand retraction of said cutting heads, f. mounting on said groovingdevice reciprocating means to reciprocate said cutting heads in thebarrel, g. moving said adjusting means to radially extend said cuttingheads so that said cutting heads abut against the interior surface ofsaid barrel, and h. actuating said reciprocating means so that saidcutting heads longitudinally score the interior of said barrel.
 5. Themethod of claim 4 including the additional steps:i. turning saidadjusting means to longitudinally move a rod associated with saidadjusting means to radially retract said cutting heads, j. unlockingsaid grooving device and rotating said grooving device to a differentrotational position, k. relocking said honing device at said differentrotational position, and l. repeating steps (g) and (h).
 6. The methodof claim 5 including the additional steps:m. again radially retractingsaid cutting heads, n. removing said grooving device from said barrel,and o. returning said screw to said barrel.